Asklemmy

I’m pretty happy with my FIIO Snowsky Mini.

It mimics a miniature Walkman and looks really great, and has a cassette playing interface that lets you totally ignore obtaining / managing album artwork. I really don’t care about seeing album art when I play music, but equally I hate seeing a ? or something when an interface expects you to have artwork. This solves that perfectly.

It’s only up to 256GB, and it only lets you scroll through all artists or all albums so navigation isn’t the quickest.

It sounds amazing. People go on about how good certain iPod classics sounded, but this is audibly better than any iPod ever was.

Doesn’t do gapless playback.

Can get them for £40-£50.

some of LG's older android phones have good builtin DAC and all the features you mention

ipods are also a good option if you can find one cheaply. the full sized models can be modded to take large storage and custom firmware

You can easily find a cheap old phone with an SD slot. If you have music downloaded then you don't need good specs, just put it in flight mode so the battery lasts longer.

Note that you might want to get something supported by the Rockbox open-source firmware, just in case the player's own software is less than ideal.

If you don't want the cost of a walkman, old LG phones like the V30 were renowned for having high quality DACs and 3.5 mm headphone jacks.

You can pick used ones up on eBay. They don't have 5g or a ton of ram so I wouldn't use it to replace my phone, but it has great audio quality and an SD card for not much money.

While researching this very thing, I came across this site hifioasisand used it to guide my first purchase.

The reviews are pretty good and they account for a lot of variables.

I bought this little speaker box from "August" that has AM/FM radio with a weather display and a USB and SD slot for external mp3 files. It mainly doubles as a bluetooth speaker but does this other stuff as well. It was under 50 bucks.

I recently got a HIFI Walker and I really like it. They also have full android versions if you want more functionality.

The audiophile community keeps them kicking around! Whathifi usually have good reviews and recs. Let me find a link

HIFI WALKER H2-128GB (or H2 Touch): This is perhaps the best match for your request. It features a, 2.4-inch screen, physical buttons for navigation, Bluetooth 5.2 for wireless headphones, and supports up to 512GB (or sometimes 1TB) MicroSD cards. It is known for high-resolution audio support (DSD, FLAC).

Surfans F20 HiFi MP3 Player: Similar to the HiFi Walker, the Surfans F20 offers a sturdy design, scroll wheel, and physical buttons. It supports up to 512GB SD cards and features Bluetooth 5.2.

Sony NW-ZX707 Walkman (64GB Internal + SD Card): While pricier, this Android-based DAP features a 5-inch touch screen, but crucially retains physical side buttons for volume and playback control. It supports MicroSDXC cards for massive storage expansion. Modded Apple iPod Classic (7th Gen): These modified classics, often sold on eBay, feature SSD storage upgrades up to 512GB, 1TB, or 2TB, and have been updated to include Bluetooth functionality and a USB-C port.

MECHEN H1 Pro / MECHEN M30: These budget-friendly options offer Bluetooth, Wi-Fi, and support for up to 512GB MicroSD cards.

I use a $50 anbernic handheld that runs a nice mp3 player, has a 3.5 jack, and has physical buttons. It is a great little ipod. This one and the ones you should consider generally have dual microSD slots and that should offer the storage you are looking for.

Can always go with a modded iPod. The great thing about digital audio is it doesn't really degrade. If you have the money to spend though the fiio's are in a league of their own at the high end.

Fiio makes some good ones. I have an old X1 that has always been flawless.

I don't have a specific recommendation, but I believe the key words to search for these days are "Digital Audio Player".

I've been following the open hardware Tangara for a while, but they're between production runs right now so you can't buy from them (you might be able to build your own though, the design is all there)

As a heads up, like so many other technologies the middle has fallen out of the market thanks to the proliferation of smart phones. You'll be paying a lot for anything decent from what I've seen

A kid i know has one from fiio, which he likes

Its small, not 512gb by itself, but features bt and sd card reader

Has physical buttons and a small display

Fiio echo mini

They probably has other models too

If you don't mind a bit of DIY tinkering you can get an older music player and upgrade it with a new battery, new drive, and rockbox. If Bluetooth is a must you could also get a 3.5mm adapter. Here is an example upgrading an iRiver player.

If you want to self-host and store the files on a home server instead of your phone, you could try out Navidrome

Edit: I guess you specified that you know there are other solutions, sorry if this was unsolicited. I have a love for physical tech too so if that’s the reason you want an mp3 player, I get it. I’m collecting records myself :)

I went through a handful of devices, and none of them ticked off all the boxes for me.

Now I use a Unihertz Jelly Star. It's tiny, it has Bluetooth, Wifi, expandable memory, headphone jack, and in a pinch it's also a phone with a camera and flashlight and so forth. The battery charges very fast, and it's got a halfway decent external speaker. More dedicated audiophiles than me would have to weigh in on if it's pumping out audio signal in all the right bass and treble frequencies at appropriate levels, but it does everything I wanted from a digital audio player.

You could try rummaging around at 2nd-hand stores or pawn shops.

Just yesterday I saw a post about using retro game handhelds as a music players. That might interest you.

I hate .mp3 as an audio codec. However, if you must use .mp3 that why not just get a used Android phone with a McroSD slot? You could even get a USB-C DAC to go with it for better sound.

The Tangara team are taking a break right now, but it's a cool project that is worth being aware of

Try Dankpods' YouTube channel, I believe he is into them and has some favourite, though I can't remember exact model numbers from the top of my head.